#79: Op Amp Power Supply Considerations: split, single, virtual ground, etc. - a tutorial

Good video!

ok peopel Im not profesional but the question is simpel I have old opel car from the 80s it uses pick up induction trigger /4pin ignition module code name mc 3334 data sheat diagram by my its cheaper model it does not have zener diode/and uses the E Core Type ignition coil. Now my goal is to finde posibiliti to advance and retard ignition timing about 10-15 ° degrees ! Now how posibli I can achive this? I did see some rc systems ,transistor and some ic chip design phase shifters but they were not reali specific and offered only set values of phase shifts like 60 120 180° degrees. So I hope for some help about that problem. Can I use external pulse generator for my hei ignition system or modifi my own phase shifter circuet? Any way any help wuld by great that thing plagues my for years I have hard cold start problems in winter .So I must alwaya fummel with distributor to turn on engine . My land does not suport those 5pin ignition modules only 7 pin modules but I dont know how to programe them externali with power suplies or relays . Any way my car is set to advance by wacum canister and counter weights so I removed all that crap I need an retarding circuet that can interfeare or manipulate ither the pick up coil out put or make programabel triggering system for the ignition module. So I reali hope some one can help my in that subject. Basicali that crapy ignition module is shit the coil saturation is terribel,it does not work on lowr engine rpm ranges and has terribel advance/retard problems . If nothing ells please some one suggest similar ic chip design ignition coil driver who is more variabel in frequency and voltage if posibel that it can operate with the pick up coil . Hope my question makes sence.

I love that you use the 741 here. This clears up a lot of questions about dual supply requirements for the 741 (and others)! Thanks for moving slowly and deliberately for us beginners. I also learned a few new things about viewing signals on Oscopes in this tutorial. Thanks for making this!

This did answer some questions! Questions that I didn't think of asking!
Do you teach the subject?
Because you seem to know possible questions students will ask.

Thank you very much for this video!

Cheers.

What a great video! The demonstrated waveforms were exactly what I was seeing. Now I know the root cause and exactly what I have to do. Thanks!

If my question was answered 9 years after the video was published the question would be out of what is indicated below:

Suppose your using a little module using a lm358 IC that was purchased out of China and pre-assembled to serve as a Mic or transducer preamp as I expect to use mine. Suppose the module has four pins with one for input from a signal source, one for output of signal from the lm358 and two pins for power supply.

Suppose you do as I did which is connect two 4 pack AA battery packs in series and supply power to the module with the free end of the one battery pack leading to Vcc and the other free end of the battery pack leading to what one might call Vee on the lm358.

The question then is what would you use as ground or the 0 volt reference point for the input and output signal?

I have used the Virtual Ground created by where the two battery packs are physically connected thus I suppose the signal swings between +6 volts and -6 volts & I have used what leads to what I have called Vee serve as the ground for the signal's input and output and see no difference on my scope under each scheme.

Any comments on this, to me, puzzle would be greatly appreciated.

Flawless presentation and demonstration of material. Thank you.

Beautiful tutorial! Thanks!

I really like the way you explain. You always go the right level of the viewers. Thank you very much for all your effort and time. Good bless you

Very useful, how can l contact you. I really need help, need to use amp in a car extra component.

Can you make a video lesson about measuring power supply rejection ratio and also power supply control loop stability? They make special probes called power rail voltage probe, which i have never used one and don't know how its so much different

I have been watching various opamp videos over the last week or 2. this is by far the best demonstration and delivery of Info on this subject I've found yet. You answered many questions I still had with both on paper and physical examples. Lemme see what else you've posted!

2022 watcher. thanks for this! helps a lot when u dont have split supply

Thanks for the great information😊

Very well explaind. Doing and showing works better then text books.

thank you. very helpful

It should be noted that the output can be isolated through a capacitor to remove the dc portion of the waveform.

Man, having the horizontal lines there makes this crystal clear for me. Always been kind of fuzzy when playing with this on my own scope. I’ll have to make sure to draw those in. Nice trick 👍

This video is so damn good, thank you!

Great video, very easy to understand, I am building an audio signal generator and you can use eiher 6 volt sprit or 12 volt single, can you tell me which way to go? Thank you kindly!!

Thanks for the great information. I was, however, hoping to learn a bit about how to calculate the power consumption of the op-amp. So.. if the output feeds say an ADC, how do we calculate the power loss through the gain resistors and the chip itself. Once again, great tutorial. Thanks.

This is an 'old' video. But a very important one!

Many people, including yours truly, blindly use an op-amp and then wondering why it is damaged or why sellers con us, we then buy some more and same story, we buy even more and same story. Lots of wondering and blaming.

Opnakp looks noisy. Noise on thtraces.

What are the advantages of using Two Diode Full wave rectification compared to using 4 diode bridge full wave rectification? The Two Diode Full wave rectification has benefits how so

What formula can you use to convert Full wave AC voltage to the Equivalent Half Wave AC voltage and vise versa? Because if a circuit needs 26vac Half wave voltage, how can you convert this to the equivalent Full wave AC voltage?

Diodes, who needs them! research androidcircuitsolver on google

Another very good video Alan. Could it be possible to show your power supplies setup and signal generator and earthing arrangements, many thanks.

In old tube amplifiers the 6vac heat voltage the transformer didn't have a center tap for the ground for the 6vac. To convert a non center tap transformer to a 6vac center tap you put two 100 ohm balanced resistors and tie them to a virtual ground which will be the tubes plate voltage. Most plate voltage are from 200vdc to 450vdc. Not sure why they would put the virtual ground to a DC potential connected to the plate voltage so that the 6vac heat voltage will have a virtual ground virtual center tap. Have you heard of this type of virtual ground?

At around the 2 minute mark, I don't think that point should be called virtual ground, unless it's a term that is used pretty loosely. Virtual ground for the op-amp would be there when you have the positive terminal connected to GND and negative feedback configuration, where the feedback action is trying to make the voltage at the negative op-amp input equal to the voltage at the positive input. In the circuit shown at the 2 minute mark, it looks like an open loop.

How to make a duel or split supply out of a single power source say a 24dc wall wart?

So if you are using the non inverting input as a voltage sensing/ smith trigger comparator mode is it still possible to use that input as a midpoint for split supply.

Im using lm358 as a compartor to turn of a constant current load when a low voltage is sensed on the non inverting input. But the Op Amp output would not turn completly off it would stay 0.8 volts above ground, the solution may be to supply it with negative voltage to swing it negetive on the output. Il give it a shot, any input of some electro wizard appriciated

Your videos are really instructive.
I decide to watch 2 vids of yours every day from now on.

Super useful!

Very nice tutorial. Thank you!

I have tried measuring the AC line noise on the primary side of various equipment on an oscilloscope but not sure how do it correctly. How can you measure the AC line noise level using an oscilloscope or is it better to use a spectrum analyzer to measure AC line noise? my Fluke DMM meter can't measure the AC line noise level so what meter would do this?

Thanks to you I finally understood why my 741 is behaving in such a weird way, liked and subscribed

Thanks Alan - like many others I refer back to your tutorials often. You balance theory and practical perfectly every time.

One thing to note here is that rail-to-rail op amps are expensive! Order of magnitude up on the likes of an LM358.

I have a 741 op amp with a 170mV, 852Hz input sine wave, +5/-5V power. I have a 10k resistor from the inverting terminal to ground and a 20k feedback resistor (output to inverting terminal), the input is on the non-inverting terminal ... the gain should be 3... but instead the gain is roughly 1. (So the output is roughly 170mV.) The output is not clipping... I'm not sure what's going on...?

Very VERY good Sir! Thank you!

Thanks for this. I am measuring AC current and feeding a 12bit adc so this was essential for my passive cct conditioning.

Great video. thank you very much.
What happened to output swing voltage if the output current is increased? how to use opamp to drive a low impedance load?

Really great tutorial. Clear and simple diagrams with a delivery style that I found very easy to follow.

BTW. Do not go too much beyond power supply range with your input. The AD8032 does support going about 200mV below (above) negative (positive) supply safely, and still maintain linearity of output vs input (obviously you would use gain less than 1 in this case usually). Above that the linearity (and distortion characteristics) can't be guaranteed. Additionally, 500mV is stated as a absolute maximum, beyond which opamp can be permanently be damaged. It is recommended to add external clamping diodes if you expect this to be possibly happening.

Super useful. Are there some performance tradeoffs to the rail-to-rail opams? Noise, bandwidth, input voltage offset, temperature stability, drive/sink output current, etc.